1. Field of the Invention
The present invention relates to a terrestrial Digital Multimedia Broadcasting (DMB) system. More particularly, the present invention relates to a terrestrial DMB receiver using an imaginary channel, in which a user defines an imaginary channel, maps a broadcasting service actually received through the imaginary channel, thereby receiving the same broadcasting service by means of the mapped broadcasting service even when a broadcasting service is provided through a different frequency due to inter-area movement.
2. Description of the Related Art
A terrestrial DMB relates to a system standard, which was introduced first in Korea, to provide a multimedia broadcasting service including video on the basis of Digital Audio Broadcasting (DAB) Eureka-147 system. DAB is a digital radio broadcasting standard used in Europe which provides both a high quality audio service of CD quality and a data service simultaneously.
When compared to the general digital broadcasting, such as Advanced Television Systems Committee (ATSC) and Digital Video Broadcasting (DVB), the terrestrial DMB is advantageous in that a user can watch broadcasting programs while moving. That is, if a DMB user has a DMB receiver terminal, the user can watch the broadcasting at any time when moved one place to another remote place.
Terrestrial DMB has another advantage in that a broadcasting service is not limited only to a video service, but offers an audio service and a data service. Accordingly, it is possible to provide more channels and services through the terrestrial DMB, as compared with the stationary terrestrial digital broadcasting scheme. A terrestrial DMB signal is formed by an ensemble, which includes multiple services. One ensemble corresponds to a basic element constituting a terrestrial DMB signal, and a user can receive a specific service by selecting a service in the ensemble. Hence, one ensemble may include multiple video services, audio services and data services.
FIG. 1 is a diagram illustrating the structure of an ensemble used in a terrestrial DMB system.
Referring to FIG. 1, the ensemble used in the terrestrial DMB system includes a plurality of services and service components constituting each service. The ensemble has a structure conforming to a DAB standard proposed by an existing Eureka-147. As illustrated in FIG. 1, the ensemble 101 with a label “DAB ENSEMBLE ONE” includes services “ALPHA 1 RADIO” 102, “BETA RADIO” 103 and “ALPHA 2 RADIO” 104. The service “ALPHA 1 RADIO” 102 includes the service components 105 to 107, the service “BETA RADIO” 103 includes the service components 108 and 109, and the service “ALPHA 2 RADIO” 104 includes the service components 106, 107, 109 and 110.
The service in the ensemble is included in a portion of one ensemble frame of Main Service Channels (MSCs) 114 to 118, and configuration information of such an MSC may be understood through Multiplex Configuration Information (MCI) 111 and Service Information (SI) 112, which are received through a Fast Information Channel (FIC).
If a receiver terminal actually selects and tunes a specific ensemble, the service included in the MSC of the ensemble is not directly extracted and displayed. That is, the MCI 111 and the SI 112 of the FIC is first analyzed, then the services of the MSC are displayed.
Hereinafter, the terrestrial DMB system used in Korea will be described. The number of ensembles assigned to the terrestrial DMB is six, and each ensemble includes multiple services.
Tables 1a and 1b show simple information on ensembles assigned to the terrestrial DMB and service information. As shown in tables 1a and 1b, the terrestrial DMB includes 7 video channels, 13 audio channels and 7 data channels.
TABLE 1aChannel OrganizationCorpo-Plan (channel name-rationbroadcasting type-UseNametransmission capacity)MethodBroadcasting FieldKBSKBS-Mobile 1-TV-Direct useSynthetic Organization548kKBS-Mobile 3-Direct useMusic-onlyRadio-128kKMMB-R-Radio-LeaseLife economy-only128k(KMMB)OZIC-Radio-128kLeaseMusic-only(CJ media)KBS-Mobile 5-Direct useSynthetic OrganizationData-220kMBCMBC DMB TV-TV-Direct useSynthetic Organization548kMBC DMB Radio-Direct useSynthetic OrganizationRadio-128kMBC EconomyLeaseEconomy-onlyRadio-Radio-128k(MBN)Arirang EnglishLease (KoreaKorean culture-onlyRadio-Radio-128kInternationalBroadcastingFoundation)MBC DMB Data-Direct useSynthetic OrganizationData-220kSBSSBS DMB TV-TV-Direct useSynthetic Organization544kSBS DMB Radio-Direct useSynthetic OrganizationRadio-128kTBS DMB Radio-LeaseTraffic-onlyRadio-128k(TBS-SeoulCity)KyunggiLeaseCulture and art-onlyBroadcasting DMB(KyunggiRadio-Radio- 128kBroadcasting)Hankyoreh DMBLeaseJob education-onlyData-Data-96k(Hankyoreh)LGT DMB Data-Lease (LGT)Leisure andData-96kentertainment-onlySBS DMB Data-Direct useNew technology andData-32knew servicedevelopment/experiment(SyntheticOrganization)
TABLE 1bCorporationChannelBroadcastingNameOrganization PlanUse MethodFieldYTN DMBYTN plus-TV-512kDirect useSynthetic(tentativeOrganizationname)TBN Korea TrafficLease (RoadTraffic-onlyBroadcastingTraffic SafetyNetwork-Radio-160kAuthority)Satio+-Ratio-160kLease (Satio)MusicYTN premium-data-320kDirect useSyntheticOrganizationKorea DMBKorea DMB TV-Direct useSynthetic(tentativeTV-548kOrganizationname)i4U-Radio-128kLeaseLife culture(Christianbroadcasting)Live4U-Radio-128kLease (MusicPubliccity media)performancemusic/culture-onlyKorea DMB data-Direct useSyntheticdata-348kOrganizationKMMBKMMB-TV-512kDirect useSynthetic(tentativeOrganizationname)KBS Mobile 2-TV-512kLease (KBS)Family culture-onlyKMMB data-data-128kDirect useSyntheticOrganization
The terrestrial DMB, as described above, has a disadvantage in that it is not possible to maintain the ensemble frequencies of all areas due to inter-channel interference. In the case of satellite DMB, one broadcasting service is provided through an equal frequency domain on a national scale. However, in the case of terrestrial DMB, broadcasting services have different frequencies according to areas. That is, even when a terrestrial DMB broadcasting signal with an index of “ensemble 1” is received in an area “A” through a frequency “a”, the terrestrial DMB signal with the index of “ensemble 1” may not be received in an area “B” through the same frequency “a”. As a frequency differs depending on the area, a terrestrial DMB receiver terminal must find information on each ensemble through an ensemble scanning.
Further, when terrestrial DMB broadcasting is received through a terrestrial DMB receiver terminal, a service category is first determined and broadcasting is selected through channel information within a corresponding service category. When broadcasting is received through a terrestrial DMB receiver terminal as described above, a selection process of broadcasting is complicated and broadcasting is not immediately selected by a user.
FIG. 2 is a diagram illustrating a process by which an existing terrestrial DMB receiver terminal selects broadcasting.
As illustrated in FIG. 2a, a user determines a service category of desired broadcasting. Such a service category may be classified into “1. video channel”, “2. audio channel”, “3. data channel”, etc. As illustrated in FIG. 2b, a user searches for the desired broadcasting through a service list within the determined service category. If the user determines the desired broadcasting, the corresponding broadcasting is output as illustrated in FIG. 2c. 
The reason for classifying each broadcasting service according to the service categories as described above is because a user cannot know the service category of broadcasting received through broadcasting channels due to the increase in the number of broadcasting channels provided from a terrestrial DMB system. Hence, it promotes the user convenience.
However, when a user searches for radio broadcasting, data broadcasting and video broadcasting, the user must repeat a search according to the service category and perform a movement of the service category as described above. Therefore, the user may feel inconvenienced.
FIG. 3 is a diagram illustrating the change of ensemble information due to inter-area movement in a general terrestrial DMB system.
Referring to FIG. 3, a service “MBC movie” is provided to an ensemble 1 of a first area 31 and a service “KBS radio” is provided to an ensemble 2 of the first area 31. A service “SBS drama” is provided to an ensemble 1 of a second area 32, and the service “MBC movie” is provided to an ensemble 2 of the second area 32. Further, the service “MBC movie” is provided to an ensemble 1 of a third area 33, and the service “SBS drama” is provided to an ensemble 2 of the third area 33.
Since ensembles are different according to areas, it is not easy for a DMB user with the mobility to select a desired service while moving between different areas. That is, with the change of the ensemble according to areas, it is not easy for the user to search for a service while moving between different areas.
As described above in FIG. 2, the DMB has many services. In selecting a specific service, most DMB users familiar with stationary broadcasting have become used to a scheme for selecting a service by directly pressing a number key mapped to the specific service. However, in a terrestrial DMB system, users cannot select a service by directly pressing a number key as in the case of the fixed broadcasting. The reason for this is as follows. In stationary broadcasting, number key information for service selection is associated with the number of a physical channel (i.e. frequency) receiving broadcasting signals. However, in terrestrial DMB, a physical channel is associated with an ensemble, and services of each broadcasting channel have a meaning as a logical channel within the ensemble. Therefore, it is not possible to match the physical channel with the number key, as in the case of stationary broadcasting.
As described above, as the conventional terrestrial DMB system does not match a service with a number key, it is impossible to use a channel selection method for selecting services by inputting a number key, as in the case of the conventional stationary broadcasting.